Positive-displacement pump



y 3, 1969 w. SCHINDLER I I 3,443,522

POSITIVE-DISPLACEMENT PUMP FiledJuly 10, 1967 Sheet of 3 I 5 5 "mum 3 I 51% 1 Q a" I *7 29 Wk 5 INVENTOR Werner Schindler y 3, 1969 w. SCHINDLER 3,443,522

POSITIVE-DISPLACEMENT PUMP Filed July 10, 1967 3s an as 22 I INVENTOR Werner Schindler u M A6695.

' Sheet Filed July 10, 1967 a a J 3 A, v// v/. /v m 9 z wwwwma 5 M .M w a mm 47% I .F I !L A a w% MR 2 3% new lNV ENTOR Werner Schindler United States Patent 3,443,522 POSITIVE-DISPLACEMENT PUMP Werner Schindler, Berghausweg, 2500 Rio], Switzerland Filed July 10, 1967, Ser. No. 652,202 Int. Cl. F04c 1/04 US. Cl. 103126 7 Claims ABSTRACT OF THE DISCLOSURE A positive displacement pump with automatic regulation of a leakage flow from its pressure side to its suction side, the leakage being controlled by the pump pressure.

This invention relates to a positive-displacement pump, particularly vane-type pump, with members rotating between a suction side and a pressure side between lateral limitations separating the pressure side from the suction side. Normally the rotating members have the form of toothed gears or rotating toothed rings. Pumps of this type are generally used for producing pressure in hydraulic control systems, such as for feeding fuel to oil burners and the like. In these applications a predetermined pressure must be built up and maintained and this requirement makes it necessary that the delivery of the pump exceeds the maximum flow in the consumer. Herewith the arrangement of a pressure regulator through which the part of the delivered liquid not used by the consumer is circulated back to the suction side of the pump becomes an obligatory requirement. These pressure regulators are relatively expensive additional parts of the system which have to be dimensioned for the full pressure and generally for the full delivery of the pump, because phases usually occur in a hydraulic control system during which no pressure oil at all is consumed.

The present invention bases on the idea to avoid the above draw-backs in that the pump itself is used for pressure regulation by a suitable construction in that a variable shunt between the pressure side and the suction side is produced in the pump itself. The pump according to this invention broadly comprises members rotating between a suction side and a pressure side between lateral limitations separating the pressure side from the suction side, the one limitation being axially shiftably arranged in the pump casing like a piston, a pressure chamber formed at the side of the shiftable limitation opposite to said members, for instance toothed gears, and at least one valve for pressure regulation in said pressure chamber. It is a result of the variable sealing action in the pump that according to the actual sealing action or the actual leakage respectively a direct flow-back from the pressure side to the suction side occurs in the pump whereby an automatic pressure regulation is possible. Due to the limitation or member of which the displacement is hydraulically controlled, a pressure regulation or a wanted control of the pressure is possible in a simple manner with the means all the same available.

The invention will now be explained in detail with reference to some embodiments illustrated by way of example in the accompanying drawing.

FIG. 1 shows a schematical cross-section through a pump for explaining the basic idea of this invention,

FIGS. 2 and 3 show each a longitudinal section through the pump in two different operating positions,

FIG. 4 shows a longitudinal section through a first embodiment of the pump,

FIG. 5 shows a section along line VV in FIG. 4,

FIG. 6 shows a section along line VI-VI in FIG. 4,

FIGS. 7 and 8 show a longitudinal section through a 3,443,522 Patented May 13, 1969 modification of the coupling of the pump according to FIG. 4,

FIG. 9 shows a longitudinal section through another embodiment of the pump,

FIG. 10 shows a longitudinal section through a modification of the pump according to FIG. 9,

FIG. 11 shows another embodiment of the pump in longitudinal section,

FIGS. 12 and 13 show a trochoid pump in longitudinal and cross-section respectively and FIG. 14 shows another pump in longitudinal section.

FIGS. 1-3 show an embodiment of a pump known per se, with a cylindrical pump chamber 1, a suction side 2 and a pressure side 3. A disc 4 made in one piece with the driving shaft 5 of the pump is rotatably disposed in the pump chamber 1. At its one face the disc 4 has a rim of axially projecting teeth 6 located outside a crescent-shaped separating wall 7 at the bottom side of the pump. A pinion 9 of which the external toothing 10 gears with the toothed ring of the disc 4 is rotatably mounted on a shaft 8 fixed in the pump casing. A pressure spring 11 supported in the casing acts on the disc 4 and applies the disc 4 against the pinion 9. With the free space of the pump chamber 1 remaining behind the disc 4, which free space is always termed pressure chamber in the following, a cylinder 13 communicates through a bore 12. A piston 14 which is applied against a sealing 16 by a pressure spring 15 for pressure-free condition of the pump is displaceably arranged in cylinder 13.

The axial width of the teeth 6 of the pinion 9 and of the separating wall 7 are exactly the same, so that for the rest condition of the pump shown in FIG. 2 the pinion 9 is located practically without clearance between the plane limiting wall 17 of the pump casing and the opposite plane limiting wall 18 of the disc 4.

Under the conditions just mentioned, namely that the pinion 9 is accommodated between the lateral limiting walls without clearance, the pump according to FIGS. 1 to 3 operates in the usual manner when the disc 4 is driven in anticlockwise direction in FIG. 1, whereby the liquid is sucked in from the left and is delivered under pressure at the right. By reversal of the rotating direction, the delivery direction may be changed. When pressure has built up on the pressure side 3, this pressure acts onto the surface 18 of disc 4 and may displace this disc 4 against the pressure of spring 11 to the right in FIG. 2. In such a position displaced to the right, the disc 4 is shown in FIG. 3. For such a displacement of the disc the liquid may flow back from the pressure side to the suction side laterally of the pinion 9. The position of the disc 4 is not only determined by the pump pressure and the force of spring 11, but the disc is disposed in the pump chamber 1 in such a leaking condition that a certain pressure is built up at the right of disc 4 in the pressure chamber mentioned above. This pressure acts through the bore 12 onto the piston 14 and pushes the same back when a determined pressure is reached. Therefore, the pressure regulation by the pump is not only controlled by the spring 11 but also by the piston 14 acting as a valve, which is pushed back and allows liquid to flow out through the outlet 19 to the suction side when the pressure in the pressure chamber at the right of disc 4 increases. Consequently an indirect pressure regulation occurs in that a pressure regulation in a pressure chamber at the right of disc 4 is effected by piston 14, and this pressure acting onto the disc 4 regulates in the first line the clearance between the disc 4 and the pinion 9 and consequently the direct shunt from the pressure side to the suction side of the pump. Thereby the spring 11 has above all the task to apply the disc 4 against the pinion 9 practically without clearance when the pump is shut down and without pressure, in order that the pump normally sucks in when started up the next time until the pressure is built up.

The clearance between the disc 4 and the pinion 9 is substantially exaggerated in FIG. 3 for the sake of a clear illustration, but in fact practically no pressure would build up with such a clearance.

The use of the indirectly acting pressure regulator 14 has the advantage that this regulator may be dimensioned for a very small fiow and also for relatively small pressures. Since the control pressure in the pressure chamber at the right of disc 4 act onto a substantially larger surface of this disc than the pump pressure existing at the pressure side, this control pressure has only to be a part, at the most about half the operating pressure of the pump. With this disposition it is also easily possible to adjust the pressure in that the pressure of the spring 15 is adjusted by well-known means. But it is also possible to provide a number of regulators adjusted to different operating pressures and adapted to be selectively connected to the pressure chamber of the pump by means of shut off valves. By way of example, a shut off valve adapted to be opened for preselection of the desired pressure may be series-connected with each pressure regulator.

In FIGS. 4-6 in which corresponding parts are similarly designated as in FIGS. 1-3, a practical embodiment of the pump is illustrated. In this case, the pump casing is flanged to a motor not fully illustrated, of which the shaft 21- is connected to the one half 22 of a coupling. The other half 23 of the coupling is attached to the driving shaft 5 of the pump. Two axial pins 24 applying against radial driving pins 25 of the coupling half 22 are connected to the coupling half 23. Preferably the one pair of coupling pins is made of plastics material and the other pair of steel in order to damp the transmission of vibration from the pump to the motor. Both coupling halves 22 and 23 may axially be shifted relatively to each other in order to take up the actual displacement of the shaft 5. In this case, the pressure spring 11 is disposed between a disc 26 fixed on the shaft 5 and a ring 27 of the stufiing box seal.

As shown in FIG. 5 the pressure spring 15 of the pressure regulator is supported on a regulating screw 28 which may be displaced after removal of the cover 29 for adjusting the desired pressure. Operation of the embodiment according to FIGS. 4 to 6 corresponds to the operation of the pump according to FIGS. 1 to 3 with the exception that resetting of the disc 4 during shut-down is effected by the spring 11 acting onto the shaft 5 instead of disc 4. Another difference resides in that a flow passage 65 is provided between the pressure side 3 and the pressure chamber 1 allowing immediate building up of pressure in the pressure chamber 1 and consequently fast regulation. Similar flow passages may be provided in all embodiments although not shown in the drawing.

FIGS. 7 and 8 show modifications of the slidable coupling according to FIGS. 4 to 6, whereby the resetting spring 11 is accommodated in these couplings. In the embodiment according to FIG. 7 the spring is directly arranged on the shaft 5 and 21 inside the coupling pins 24 and 25, whereas in the embodiment according to FIG. 8 it is located outside the coupling halves. The solution according to FIGS. 7 and 8 has the advantage that the spring has not to be arranged in the pump between a rotating and a stationary part, but between both coupling halves rotating at the same speed.

The embodiment according to FIG. 9 substantially corresponds to that of FIG. 4, whereby however the resetting spring 11 is not located in the stuffing box but in the pump chamber 1. The spring acts on a collar 30 of a sleeve 31 which is secured against rotation by means of a pin 33 engaging into a slit 32, but which is displaceable in axial direction. In this case the sleeve 31 may serve as a bearing for the shaft. An axial antifriction bearing 34 is inserted between the collar 30 of the sleeve 31 and the disc 4 of the pump rotor, through which the actual pressure of the sleeve 31 is transmitted to the disc 4. Opera- 4 tion of the pump according to FIG. 9 corresponds to that of the pumps described above.

In the modification according to FIG. 10, the resetting spring 11 is arranged between a sleeve 35 seated on the driving shaft 5 and a ring of an axial anti-friction bearing 36, in which case the sleeve 31 may be dispensed with.

Another modification is illustrated in FIG. 11, in which not the disc 4 of the driven pump rotor but the opposite limitation is axially displaceable. This opposite limitation 40 is disposed axially displaceable and secured against rotation in the pump chamber 1 in the manner of a piston and is pressed by the spring 11 against the adjacent face of the toothed ring 6 and of the pinion 9. The shaft 8 of the pinion 9 is fixed in the limitation 40. The communicating bore 12 to the pressure regulator communicates with the pressure chamber formed at the left of the limitation 40.

Operation of the pump according to FIG. 11 corresponds to the operation described above, whereby the difference resides in that regulation of the flow-back from the pressure side to the suction side is effected by axial displacement of the piston-like limitation 40 relatively to the axially undisplaceable disc 4. The manner of pressure regulation corresponds completely and needs no further explanation.

A trochoid pump is shown in FIGS. 12 and 13, of which the inner gear 50 is driven from the driving shaft 5 by a driving pin 51. The inner gear 50 drives the internally toothed outer rim 52 rotatably mounted in the pump chamber. The delivery chamber formed between the inner gear 50 and the outer ring 52 is limited at the left by the plane casing wall 53 and at the right by the face of a ring 54. The ring 54 is axially displaceable in a ring-shaped chamber of the casing and is applied against the face of the rotating pump parts by the resetting spring 11. The pressure chamber formed at the right of the ring 54 communicates through the bore 12 with the pressure regulator for which the liquid flows back through the outlet 19 to the suction side 2. In this case the regulating part 55 of the pressure regulator is constructed somewhat difi'erently. It has a through bore 56 and regulation of the flow is effected at the upper face of the part 55 acting as a valve seat.

Operation of the pump according to FIGS. 12 to 13 corresponds again to that of the pumps described above. Under the action of the pump pressure the ring 54 is shifted to the right against the action of spring 11 and the pressure in chamber 1, so that at the side of the rotating parts 50 and 52 a direct flow-back from the pressure side to the suction side may occur. The position of ring 54 is thereby automatically so adjusted that the pressure forces acting from the left and from the right are balanced whereby a pressure regulation takes place in the manner described.

FIG. 14 shows another embodiment of the pump with two spur gears 60 and 61 meshing with each other without clearance. The driving gear 60 is fixed on the driving shaft 5 and drives the gear 61. The pumping action takes place in a manner well-known per se. One side of the driving gear 60 engages a sealing sleeve 62 onto which the schematically illustrated resetting spring acts. An antifriction bearing 63 is disposed between the sleeve 62 and the gear 60. The pressure chamber formed at the right outside the sleeve 62 communicates through the bore 12 with the space 64 of the pressure regulator not shown in detail.

Operation of this embodiment substantially corresponds to the already described operation of the other embodiments. In the rest condition of the pump the pressure side and suction side are sealed from each other in that the sealing sleeve 62 is sealingly applied against the gear 60 by spring 11. Therefore the pump normally sucks in but after building up of the pressure the sleeve 62 is shifted to the right in accordance with the pressure difference and causes a direct shunt between the pressure side and the suction side of the pump. Regulation of this effect by the pressure regulator corresponds to that described above.

Besides the functional advantages already mentioned the illustrated pumps also have substantial constructive advantages. Up to now care had to be taken by accurate tolerances that the pump chamber was practically tightly sealed on all sides that is, for example, that in the embodiment according to FIG. 4 the outer rotor of the pump should rotate in the pump chamber in absolutely sealing condition and that the surfaces laterally limiting the rotating gears should really limitate these gears without clearance. Only in this way it is possible to avoid uncontrollable leakage losses between the pressure side and the suction side. Contrary to this, wide tolerances may be allowed in the illustrated pumps because under normal operating condition a back flow from the pressure side directly to the suction side occurs all the same and further leakage of the pressure liquid from the pressure side to the back side of disc 4 is desirable in order to obtain the pressure regulation according to this invention.

As already mentioned the pressure regulator may be influenced as wanted by adjustment or other action, whereby for instance in the manner already mentioned a number of pressure regulators fixedly adjusted are connectable selectively. With this arrangement the advantage further results that upon change from one pressure level toanother regulation does not occur suddenly, because the actual displacement of disc 4 or a corresponding part occurs with a certain inertia.

It is also possible to provide a so-called progressivepressure regulator which may be brought into the desired adjustment, for instance by means of a cam disc and a servomotor. Hereby the particular advantage results that due to the limited pressure and the limited flow of the pressure regulator operation is possible with very low control power.

In certain applications it may be desired to completely reduce as soon as possible the pump pressure while the pump continues to rotate. For this purpose the pressure chamber of the pump in which the control pressure exists may be directly connectable to the suction side through a release valve, for instance an electro-valve, so that the control pressure suddenly completely breaks down when this valve is opened, whereafter the pump pressure falls off to a very low rest pressure determined by the pressure of spring 11. Such a pump may preferably be used as a feeding pump of an oil burner where it is desired to suddenly stop the oil pressure when the burner is shut down.

What I claim is:

1. A positive-displacement pump comprising eccentrically mounted gears externally and internally toothed respectively and a crescent portion of the casing engaging between such gears at one side, said internally toothed gear having a disc fixedly mounted on a driving shaft and teeth axially extending from said disc, and said disc axially engaging said externally toothed gear, said disc and driving shaft being axially shiftable in the pump casing, coupling means having a first coupling portion mounted on said driving shaft and a second coupling portion axially shiftable relatively to said first coupling portion and mounted on a motor shaft, a pressure chamber formed at the side of said disc opposite the teeth of the internally toothed gear, a pump inlet and a pump outlet, and an adjustable overpressure valve connected between said pressure chamber and pump inlet and operable by the fluid in said pressure chamber for maintaining the pressure in said pressure chamber at a predetermined value and axially urging said disc against said externally toothed gear at a predetermined pressure.

2. A pump according to claim 1, characterized in that the disc is accommodated in the bore of the casing in incompletely sealing condition.

3. A pump according to claim 1, characterized in that a spring is provided in the coupling for applying the rotatable disc against the externally toothed gear.

4. A pump according to claim 1, characterized in that the spring is disposed between a casing portion and the one rim of an axial antifriction bearing, of which the other rim is supported at the driving shaft or at the rotatable disc.

5. A pump according to claim 4, characterized in that the spring is located in the stuffing box or in a sleeve surrounding the driving shaft and secured against rotation.

6. A positive-displacement pump comprising eccentrically mounted gears externally and internally toothed respectively and a crescent portion of the casing engaging between such gears at one side, said internally toothed gear having a disc fixedly mounted on a driving shaft and having teeth axially extending from said disc and said disc axially engaging said externally toothed gear, said disc and driving shaft being axially shiftable in the pump casing, a pressure chamber formed at the side of said disc opposite the teeth of the internally toothed gear, a pressure chamber formed at the side of said disc opposite the teeth of the internally toothed gear, a pump inlet and a pump outlet, and an adjustable overpressure valve connected between said pressure chamber and pump inlet and operable by the pressure built up in said pressure chamber during pump operation, this pressure being thus maintained at a predetermined value and said disc being pressed against said externally toothed gear with a predetermined force.

7. A positive-displacement pump comprising toothed gears rotating between a pump inlet and a pump outlet, axially displaceable limiting means axially urged against the one face of at least one of said toothed gears for laterally sealing said gears between said outlet and inlet, a pressure chamber formed at the side opposite to said gears of said limiting means, fluid passage means for limited fluid leakage from said pump outlet into said pressure chamber and an adjustable overpressure valve connected between said pressure chamber and said pump inlet and operable by the pressure in said pressure chamber thereby maintaining the pressure in said pressure chamber at a predetermined value for axially urging said limiting means against the one face of at least one of said gears at a predetermined pressure.

References Cited UNITED STATES PATENTS 1,853,430 4/1932 Jensen. 1,877,688 9/1932 Petersen. 1,944,648 1/ 1934 Saussard. 2,079,375 5/ 1937 McCollum. 2,405,061 7/ 1946 Shaw. 2,437,791 3/1948 Roth et al. 2,627,232 2/1953 Lauck. 2,786,553 3/1957 Boone et al. 2,787,963 4/ 1957 Dolan et al. 2,915,977 12/1959 Campbell.

DONLEY J. STOCKING, Primary Examiner. W. J. GOODLIN, Assistant Examiner. 

